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CVE-2021-21424

Symfony is a PHP framework for web and console applications and a set of reusable PHP components. The ability to…

Summary

Vulnerability reported (CVE-2021-21424). Risk of unauthorized operations or information disclosure.

Original description

The description as published by the source.

Description

The ability to enumerate users was possible without relevant permissions due to different exception messages depending on whether the user existed or not. It was also possible to enumerate users by using a timing attack, by comparing time elapsed when authenticating an existing user and authenticating a non-existing user.

Resolution

We now ensure that 403s are returned whether the user exists or not if the password is invalid or if the user does not exist.

The patch for this issue is available here for branch 3.4.

Credits

I would like to thank James Isaac and Mathias Brodala for reporting the issue and Robin Chalas for fixing the issue.

Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2021-21424 has been found.
Risk of unauthorized operations or information disclosure.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "CVE-2021-21424" on the vendor's site.

CVE-2021-21424
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (unclassified) has been reported.

📍 Affected scope

Check the vendor advisory for the affected versions.

🔥 Severity

Severity: ?. Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    Audit SBOM/dependencies for affected components.

    資産台帳・SBOM・依存マニフェストで影響コンポーネントを特定する。

  2. 2
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

Packagist symfony/security
[{"type":"ECOSYSTEM","events":[{"introduced":"4.0.0"},{"fixed":"4.4.24"}]}]
Packagist symfony/security-guard
[{"type":"ECOSYSTEM","events":[{"introduced":"5.0.0"},{"fixed":"5.2.8"}]}]
Packagist symfony/security-core
[{"type":"ECOSYSTEM","events":[{"introduced":"5.0.0"},{"fixed":"5.2.8"}]}]
Packagist lexik/jwt-authentication-bundle
[{"type":"ECOSYSTEM","events":[{"introduced":"2.11.0"},{"fixed":"2.11.3"}]}]
Packagist symfony/maker-bundle
[{"type":"ECOSYSTEM","events":[{"introduced":"1.30.0"},{"fixed":"1.31.1"}]}]
Packagist symfony/security-http
[{"type":"ECOSYSTEM","events":[{"introduced":"5.1.0"},{"fixed":"5.2.8"}]}]
Packagist symfony/symfony
[{"type":"ECOSYSTEM","events":[{"introduced":"5.0.0"},{"fixed":"5.2.9"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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